1. Field of the Invention
A foot operable controller for a surgical instrument and, more particularly a, foot operable controller for an ophthalmic surgical instrument
2. Prior Art
Foot operable devices for controlling surgical instruments are well known and represented in the art. In the treatment of cataracts, a phacoemulsification instrument is widely used for the fragmentation and removal of a crystalline lens prior to replacing the defective lens with an artificial lens. Such an apparatus requires the administration of a preferred level of ultrasonic energy to the lens and the introduction of an irrigation fluid stream to the operative site and the removal of fragmented tissue from the operative site via an aspiration vacuum. Accordingly, in order to free the surgeon's hands, control signals are supplied to the instrument via a foot operable controller. The foot operable controller includes independent means for generating both proportional and/or fixed control signals for establishing the desired ultrasonic power level, irrigation fluid flow and varying the aspiration vacuum pump in response to foot movement.
Various systems have been used to control surgical instruments in general, and phacoemulsification equipment in particular. For example, one approach used a foot-operated controller to control a surgical instrument wherein azimuthal rotation of an operator's foot selects a function from a menu. After the function is selected, the foot-pedal is returned to a center position and depressed (or elevationally moved) to generate a control signal for the selected function. The rotational azimuthal movement of the pedal does not provide a displacement-proportional control signal and the foot pedal could not be rotated and depressed at the same time.
Another approach to providing control signals using a foot activated controller utilizes a digital electronic foot operable controller comprising a rotatable shaft affixed to a foot pedal. The shaft includes a shaft encoder, which provides a digital signal related to the rotational status of the shaft. The output signal from the shaft position encoder is input to a control card, which uses the signal to control various functions of the medical apparatus.
Yet another system employing a foot pedal controller has a rotatable arm having three spaced conductors on a surface thereof. The arm rotates over regions bearing spaced pairs of electrodes; each pair of spaced electrodes corresponding to a different function. Thus, rotation of the foot pedal can be used to turn on the flow of irrigating fluid to an irrigating channel in a phacoemulsifier hand piece, apply a vacuum to an aspiration channel in the hand piece and deliver ultrasonic power to the hand piece. Another example uses a dual position foot pedal control unit that includes a base and a pedal arrangement that enables a user to generate control signals using his/her toe and sole. Switching between the dual positions is accomplished by rotation of the foot-pedal. The controller enables a user to switch between two different functions by rotating the foot to generate a control signal for the function by either sliding the foot pedal with respect to the base or depressing the foot-pedal.
Foot control devices have also been used to control other types of instruments. For example, one foot controlled device was used to generate control signals for a zoom microscope. Vertical movement of the foot pedal brings the image into focus while rotation of the foot pedal changes the magnification in a displacement-proportional manner. In addition, the foot pedal may be moved reciprocally in a plane parallel to the azimuthal plane and orthogonal to the direction of vertical motion to change the field of view.
In a phacoemulsification system, aspiration vacuum developed by the system is modulated by a foot operable controller to increase or decrease suction at the tip of the operating instrument from zero to a desired level. Additionally, the foot operable controller may also be switchable between a fragmentation mode which is used to control the phacoemulsification module and hand piece and a cutter mode which is used to control operation of a micro surgical cutting instrument. When the selector is set to fragmentation, and the infusion mode of the infusion/aspiration module is set on auto, depressing the foot pedal to a first position, signaled by an audible click, activates infusion to the handpiece. Depressing the foot pedal to a second position, signaled by a second click, activates both infusion and aspiration. Depressing the foot pedal to a third position activates infusion, aspiration, and phacoemulsification.
During phacoemulsification, the surgeon is concentrating on performing microscopic movements of the phacoemulsification probe within the eye. Such movements are guided by the surgeon by viewing the eye through a high power surgical microscope. Typically, the surgeon will not want to disengage his view from the microscope to look at the panel of the instrument to determine what mode the instrument is in, or what power levels or aspiration levels are being used. For this reason, various attempts have been made to provide a foot operable controller that provides some form of sensory feedback to the surgeon so that he or she may determine the mode and settings of the machine while maintaining their view through the surgical microscope.
One attempt at providing feedback to the surgeon using a foot operable controller provides a plurality of resistance forces which are staged to provide increasing resistance at predetermined points along the rotational travel of the foot pedal. Thus, the foot pedal provides different tactile feedback for each of the different ranges of operation. Foot pedals utilizing this method of providing feedback typically provide two or more resistance ranges as the foot pedal is depressed. Typically, foot pedals of this type provide for increasing ranges of resistance, such as may be achieved by utilizing one spring for the first range, and then another spring, which may or may not be a stronger spring, for the next range and so forth. However, such systems usually provide no warning that the next range is about to be entered, thus small adjustments in pressure on the foot pedal may cause unwanted changes in the function or power level of the phacoemulsifier.
There remains a need for a foot operable instrument control device which includes means for alerting the operator that further movement of the foot in the up/down or side to side direction will result in the change of a control signal to the instrument. Such a warning alert enables the operator to move his/her foot freely over certain ranges of motion without being concerned about changing the signal. When the surgeon is ready, the foot is moved to a position where a tactile response alerts the operator that further foot movement will change an instrument control signal. This tactile response needs to provide an equally strong alert to the operator both during foot pedal depression and elevation.